Parts treating and coating apparatus



June 20, 1961 A. c. scHouw 2,989,027

PARTS TREATING AND COATING APPARATUS Filed Dec. 19, 1957 4 Sheets-Sheet1 INVENTOR. ARTHUR C. SCHOUW ATTORNEY.

June 20, 1961 A. c. scHouw PARTS TREATING AND COATING APPARATUS 4Sheets-Sheet 2 Filed Dec. 19, 1957 o 4 ID a A w T 2 8 20 0 m 4 40w7 88 92 06 l 2 6 2 Mw m. 0 M4 A T l 9 M 4 .6 H. e w w m 3 2 H v a "H 2 W w n am A 4 w M 820 o 8 a m 88 w 2 u w E r f w 7 Z 5 M 3 M l 6 0 a 6 w H H w1|!I A i T L WM 84 0 M H I INVENTOR. ARTHUR C. SCHOUW ATTORNEY.

June 20, 1961 A. c. scHouw 2,989,027

PARTS TREATING AND COATING APPARATUS Filed Dec. 19, 1957 4 Sheets-Sheets Fig. 4

LA [RM INVENTOR. ARTHUR C. SCHOU W A T TORNEV.

June 20, 1961 A. c. scHouw 2,989,027

PARTS TREATING AND COATING APPARATUS Filed Dec. 19, 1957 Y 4Sheets-Sheet 4 70 q A 4' 'I/III/I/IIIIII/Ii/ j Ill 90 Fig. 5.

INVENTOR. ARTHUR C. SCHOUW ATTORNEY.

limited States This invention relates generally to apparatus fortreating metallic parts and particularly to apparatus for washing andcoating metallic parts to protect them against corrosion.

As is well known, the usual solution to the prevention of corrosion ofmetal product parts, particularly steel parts, is to plate them with anon-corrosive metal. While this method is essential for the parts ofcertain products, particularly those exposed to the elementsout-of-doors, it is a very costly procedure. For products such asbusiness machines, the cost of plating the many parts is prohibitive,yet corrosive action occurs although such machines are not subjected tothe outdoor elements and such corrosion is, of course, undesirable. Ihave found that corrosion of metallic objects is due largely toattraction to the surfaces thereof of minute particles of soil whichbuild-up and by bacteria chemical action initiate corrosive and rustingactions, and that this action can be inhibited for a long period by aninexpensive process that may be carried out by my improved parts washingand drying apparatus.

Accordingly, it is an object of my invention to provide an improvedapparatus for treating metallic parts to protect them against corrosion,without the need and expense of plating the parts.

Another object of the invention is to provide an improved apparatus forwashing metallic parts and protecting them against corrosion by bakingthe residue of the washing compound containing corrosion resist materialonto the parts as the protective coating.

Another object of the invention is to provide an improved apparatus ofthe above mentioned character in which heat necessary to the washing andtreating of the parts against corrosion is generated internally and byoperation of the apparatus.

Specifically, it is an object of my invention to wash metallic partswith a cleaning compound and simultaneously with the removal of excesswater from the parts, apply heat to the parts in such a manner as tocause a film of the cleaning compound residue to contract about andenvelop the part as a protective coating against corrosion.

Another object of the invention is to provide an improved parts treatingapparatus in which fluid jet streams directed to impinge againstopposite faces of the parts to clean and dry the parts, and which wouldordinarily bounce the parts about, causing nicks therein, are instead,utilized as means of positively holding the parts down against theconveyor.

In connection with the next preceding object, it is a further object toprovide an improved and convenient arrangement for changing the fluidpressure differential for accommodating parts of different size ordifferent weight, or both.

A further object of the invention resides in the introduction into thecleaning compound of a wetting reagent to insure a complete film of thecorrosive resisting compound residue over the entire surface of the partpreliminary to drying the film.

Other objects of the invention 'will become apparent from the followingdetail description, taken in connection with the accompanying drawings,in which;

FIG. 1 is a side view, partly broken away and in secof my invention;

atent Q r 2mm lQe Patented June 20, 1961 FIG. 2 is a cross sectionalview, taken along the line' 2-2 of FIG. 1;

FIG. 3 is a horizontal cross sectional view, taken along line 3-3 ofFIG. 2;

FIG. 4 is a vertical cross sectional view, taken along the line 4-4 ofFIG. 1;

FIG. 5 is a fragmentary view of one end of the apparatus, partly brokenaway and in section;

FIG. 6 is a fragmentary cross sectional view, taken along the line 6-6of FIG. 5.

Referring to the drawings by characters of reference, the parts treatingapparatus shown includes a housing 20, a parts washing apparatus 22, aparts treating and drying apparatus 24 and a parts carrying conveyor 26.The parts washing apparatus 22 and the parts drying apparatus 24 arearranged within the housing 20, and the conveyor 26 extends through thehousing carrying the parts to be cleaned and treated.

The housing 20 may be a box-like structure having side walls 32, 34, endwalls 36, 38 and a top wall 40. Vertical partitions 42, 44 spacedlongitudinally of the housing divide the interior thereof into a partswashing chamber 46 and a parts drying and heat treating chamber 48, thechambers 46 and 48 being separated by a drain chamber 50. In the housingend walls 36 and 38, are inlet and outlet openings 52 and 54,respectively, for passage therethrough of the conveyor 26. Below theconveyor 26 within housing 20, is a tank or reservoir 60 for apredetermined quantity of water containing a cleaning compound forwashing the parts passing through the housing on conveyor 26. The tank60 preferably extends laterally from the housing side 32, and has ahinged lid 62 to provide ready access to the tank 60 for inspection andto add cleaning compound to the water.

Disposed within the parts washing chamber 46 is an upper spray head 64and a lower spray head 66 of the parts washing apparatus, and disposedwithin the parts drying chamber 48 is an upper air discharge head 68 andlower air discharge head 70 of the parts drying and heat treatingapparatus. The conveyor 26 is of the continuous type having an upperlead side that carries the parts to be washed and treated, the lead sidepassing between the upper and lower heads of the washing and dryingapparatuses.

The conveyor 26 includes a continuous wire mesh belt 74 that travelswith and between a pair of laterally positioned, parallel chains 78,which travel about sprockets at opposite ends of housing 20. Extendingthrough the housing 20 is a pair of laterally positioned parallelsupports 82 which project beyond the opposite housing end walls andsupport the sprockets 80 on shafts 84 and 86, the shafts being rotatablysupported in bearing plates 88, secured to the opposite sides of thesupports 82 outwardly thereof. Preferably both the top or lead side ofthe belt 74, and the bottom or trailing side, are supported on thehorizontal legs of angle members 90, on which the chains 78 slide. Theangle members are secured to the sides of the supports 82 inwardlythereof, such as by welding. The shaft 86 is the driving shaft of theconveyor and may be driven by means of an electric motor 92 throughsuitable speed reduction mechanism.

A plurality of spaced cross members 94 connect the wire mesh belt 74 tothe chains 78, as is shown more clearly in FIG. 6, and provide addedsupport for the belt throughout the length thereof. Each of the links ofthe chains 78 has an inwardly directed extension lug 96 to which theopposite ends of the cross members 94 may be riveted, or be otherwisesuitably secured. Extending transversely of the belt 74 on the undersidethereof, the cross members 94 may be secured by screws 98 or othersuitable means to the belt. The belt 74 is preferably of the so-calledbasket type having side flanges 3 100to retain the parts on the belt.These belt flanges are preferably enclosed by guards 102 on the supports82 and provided with downturned flange portions 104 that positioninwardly of the belt flanges in spaced relation thereto.

Submerged in the wash water in tank 60, is a ce'ntrifugal pump 106 ofsufficient capacity to deliver the wash water to the spray heads 64, 66under pressure. The pump 106 together with the spray heads 64, 66 andtank 60 form a closed circulatory system for the wash water which, afterimpingement against the parts to be cleansed, gravitates back to thetank 60. The soil and other foreign matter removed from the parts isfiltered against entry to pump 106 by a removable screen 108 in tank 60,the screen 108 overlying an opening 110 in a separator partition 112between the screen 108 and pump 106. The pump 106 has the usual intake114 and outlet 115. Preferably an electric motor 109 is used for drivingthe pump 106 the motor and pump being connected by a shaft 116.

In order to clean the parts properly and efiiciently, I have found thatthe wash water temperature should be above room temperature, but lowerthan the temperature which would destroy the effectiveness of thecompound. I have found that an efficient Washing job is obtained whenthe wash water temperature is maintained at from about 90 to 100 degreesFahrenheit and that the heat necessary to maintain such temperatures canbe generated by circulation of the wash water. Accordingly, I haveprovided for increasing the temperature of the wash water to a degreefor efficient cleaning of the parts and in the present instance withoutneed of extraneous heating apparatus and accompanying maintenanceproblems. To accomplish this, the wash water is delivered by the largecapacity pump 106 from tank 60 to the spray heads 64, 66 at a greaterrate than the rate of discharge of the water from the heads, whereby toeffect a back pressure on the pump 106 with accompanying molecularagitation of the water and corresponding generation of heat. Inaddition, I connect the outlet 115 of the pump 106 to the spray heads64, 66 by a sinuous conductor 118 which by its several turns bafilesflow of the water to head 64 with accompanying generation of heat. Theheat so generated is stored and conserved by using a closed circulatorywash water system. The system contains a predetermined amount of thewash water which is recirculated through the closed circulatory systemto retain the heat generated, which heat is stored in the relativelylarge body of water in tank 60. Water is added to tank 60 only when thelevel thereof decreases due to drip losses, vaporization, etc., to apredetermined level, whereupon water may be added to the tank 60 from asupply pipe 120 under con trol of a suitable float operated valve (notshown). A shut-off valve 122 may be provided in the water supply pipe120.

From the pump outlet 115, the sinuous conductor or pipe 118 extendsacross the tank 60 having a water shown, to effect impingement of thewash Water against the undersides of parts on the conveyor belt 74. Theupper spray head 64 is similar to the above described lower head 66, butcomprises a pair of laterally positioned, horizontal headers 134communicatively connected by branch headers 136 in each of which issecured a plurality of spaced nozzles 138, directed downwardly at theconveyor 26. The upper spray head 64 differs further from the lowerspray head 66 in that the upper head is movable vertically to change thedownward force of impingement of the wash water against the uppersurfaces of the parts, and to adjust the head to larger or smallerparts, as the case may be. In order that the upper spray head 64 may beraised and lowered, the head is connected to the vertical pipe 126 by aflexible conduit or hose 133. In the header 130 is a manually operablevalve 131 and in pipe 126 above header 130 is a similar valve 135. Thesevalves 131 and 135 may be adjusted and set to effect a pressuredifferential between the upper and lower spray heads.

Referring now to the parts drying and heating apparatus 24, thisapparatus comprises, in general, a plenum chamber 140, the upper andlower air discharge heads 68 and 70, and an air blower 142. The plenumchamber is disposed within the housing 20 together with the heads 68 and70, and the blower 142 may be mounted on a reinforcing base 144 on topof the housing. A suitable electric motor 146 may be used to drive theblower 142 by means of a belt or other drive connection. In the top wall40 of the housing 20, the plenum chamber 140 has an inlet 148, connectedto the outlet of blower 142 by a duct 150, and Within the housing '20 isa plenum outlet chamber 152 from which air is returned to the blowerintake by a return duct 154. This arrangement of the air circulatingcomponents provides a closed air circulatory system in which the air ispressurized in the plenum chamber 140 under high pressure withaccompanying generation of heat that is largely retained by the closedsystem. The temperature of the recirculated air may be controlled by theprovision of a damper .156 in a fresh air intake 158 that may beprovided in the air return duct 154. The temperature of the air ismaintained sufliciently high so that the heat will bake a film of thecompound residue onto the parts, but is maintained at a lowertemperature than that which would destroy the residue film. Atemperature of 100 to 110 degrees Fahrenheit of the air in the closedcirculatory system.

The plenum chamber 140 is separated from its outlet chamber 152 by anupper horizontal partition 160, and a lower horizontal partition 162,joined by a vertical partition 164. The horizontal partitions 160, 162extend from housing side wall 32 partway across the housing to thevertical partition 164 which is spaced inwardly from housing side wall34 to provide a connecting passageway 166 between the plenum chamberinlet 148 and a lower leg 168 of the plenum chamber 140. As shown, thelower leg 168 of the plenum chamber 140 positions between the upper andlower sides of belt 74, and the top wall of the plenum chamber leg 168serves as the lower air discharge head having a plurality of nozzles 170secured therein and directed so that the air impinges against theundersides of the parts on the conveyor.

The upper air discharge head 68 comprises a plate-like support thatoverlies the upper side of belt 74, and secured in and to said plate isa plurality of downwardly directed air jets or nozzles 171 arranged sothat the air discharging therefrom impinges against the upper surfacesof the parts on the conveyor. The upper air discharge head 68 is madevertically adjustable so that, for example, it may be raised forclearance purposes when larger parts are to be treated. To this end, thehead 68 is connected by a bellows 172 to an inlet 174 in the plenumchamber partition 160. An upwardly extending peripheral flange 176 onhead 68 is provided for connection with the lower end of the bellows 172and any suitable type of fastener, as at 178, may be used to attach thelower end of the bellows 172 to the flange 176. The upper end of thebellows 172 may be similarly connected to a metallic ring 180 which maybe secured by bolts or other suitable means to the underside ofpartition 160. Thus, pressurized air from the plenum chamber 140 andinterior of the bellows 172 is forced out of the nozzles 171 to impingeagainst the assess? upper" surfaces of the parts, the air passing intooutlet chamber 152 for return to the blower 142.

In order to maintain a high air pressure in the plenum chamber 140 withaccompanying high molecular agitation and corresponding generation ofheat, the blower 142 is preferably a high capacity rotary blower. Asshown, the blower 142 has a scroll type housing provided with an inlet181 at one side in communicationwith the return duct 154, and atangential outlet in commu nication with the plenum chamber inlet duct150. In operation of the blower 142, considerable moisture entrained inthe air from operation of the washing apparatus tends to collect in theblower housing, and to avoid interference with the blower, and also toretrieve the wash water, a drain 183 is provided from the blower housingto the drain chamber 50.

As in the washing apparatus, it is desirable that fluid impingementagainst the parts does not cause the parts to bounce about, as thisordinarily tends to deface or nick the parts, and so I provide apressure differential between the upper air discharge head 68, and thelower discharge head 70 to hold the parts down against the conveyor belt74. To this end, a damper 182 is pro vided in passageway 166, and isadjusted such that the pressure in the lower leg 168 of the plenumchamber 140 is lower than the pressure above the damper 182, thusproviding a pressure differential in favor of the upper nozzles 171.Although raising of the upper air discharge head 68 will decrease thepressure against the upper surfaces of the parts, the diflerentialpressure established by the damper 182 may be made sufiiciently largewith respect to the adjustment range of head 68, so that the damper 182may be used as a fixed setting.

Mounted on the opposite end walls 36 and 38 of the housing is avertically movable support 184 for both the upper wash water spray head64 and the upper air discharge head 68. The support 184 extends entirelythrough the housing 20 from end to end thereof, directly above the upperor lead side of the conveyor belt 74. By raising or lowering the support184, the upper spray head 64 and air discharge head 68 may be positionedcloser to, or farther away from the parts on the conveyor belt. Asshown, the support 184 is positioned within the basket-like conveyorbelt 74 and, in addition to supporting the heads 64, 68, functions as acover for the conveyor to insure that the parts are retained on the beltin the areas where the parts enter the drain compartment 50, and wherethe parts approach entrance into the drying chamber 48. Opposite ends ofthe support 184 are secured respectively to vertically movable closureplates 186 that respectively. partially. overlie the housing inlet 52and outlet 54, the plates 186 being guided for vertical movement onrollers 188. A system of cables and pulleys 190 connected to the plates186, may be used to raise and lower the support 184, and therefore heads64 and 68 with the aid of a counterbalance or weight 192. Carried byeach of the end plates -186 is a flexible closure 193, preferably asheet of rubber which overlies the housing openings through which theconveyor extends. These closures are provided to decrease loss of heatgenerated by the blower 142, and a similar closure 195 may overlie theopening in partition 44. Closure 195 is provided to decrease flow ofwater vapor from the parts washing apparatus to the parts dryingapparatus.

Since the support 184 is disposed between the upper fluid dischargeheaders 64, 68 and the parts carying belt 74, the support is fluidpervious, preferably a heavy gauge screen. Along its opposite sideedges, the support 184 has margins thereof clamped between thehorizontal leg of an angle member 194 and a lower clamp strip 196 bybolts 198. To the vertical legs of the angle members 194 is secured theair nozzle head 68 (see FIG. 6), such as by bolts 200. Similarly, theupper head 64 of the washing apparatus is mounted on the support 184, asis shown more clearly in FIG. 2. in this con struction, a pair of angle,brackets 282 are secured respectively to the upright legs of the anglemembers 194 having horizontal legs on which the spray head 64 ismounted. Any suitable fasteners may be used to securethe spray head 64to the brackets 202, such as U-bolts 204.

Any suitable well known parts washing compound may be used that includesa corrosion inhibitor, such as sodium chromate, a bactericide, a solventto prevent caking of the compound and a wetting agent to cause theresidue of the compound to spread over the entire surfaces of the parts.

Operation In operation of the apparatus, parts to be treated may be fedmanually or otherwise onto the feed end of the conveyor 26 and arecarried thereby first into the washing chamber 46. As the parts passbetween the upper and lower spray heads 64 and 66, both the upper andlower surfaces of the parts are impinged by the wash water dischargingfrom the nozzles 132, 138. The impingement force of the wash wateragainst the surfaces of the parts, aided by the cleaning compound,removes all soil from the parts as they pass through the wash chamber.During this washing operation, the parts instead of being tossed aboutby the high velocity sprays, are held down against the conveyor byreason of the pressure differential of the spray heads 64 and 66. Fromthe washing chamber 46, the parts are carried by the conveyor into thedrain chamber 50, wherein excess wash Water drips from the parts intothe reservoir tank 60 below. The parts now enter the drying and heatingchamber 48, wherein the air blows most of the remaining moisture fromthe parts, there being a film of the wash water and cleaning compoundresidue remaining on the parts. This film containing the corrosioninhibiting elements of the compound and bactericide flows or is causedto spread over the entire surfaces of the parts by the air pressure andby reason of the presence of the wetting reagent in the compound. Thismeans that the wash water residue enters and covers the surfaces of theminute peaks and valleys of the parts thereof, and thus, completelyenvelops the parts with a film that provides a barrier to atmosphere. Atthe same time that the air blows excess moisture from the parts, theheat contained by the air is applied thereby to bake the film of washingcompound residue onto the part, the film contracting and hardening bythe application of the heat. This results in a coating of corrosiveresisting material on the parts which will protect the parts for aconsiderable period.

From the foregoing description, it will now be appreciated that I haveprovided an improved apparatus for inexpensively providing metal objectswith a skin of corrosive resist material from the residue of the washoperation. By having the corrosion inhibitor in the wash water andspreading the wash water as a film residue including the inhibitor overthe entire surface of the obiect or machine part, and then baking thefilm onto the parts, a very effective corrosion inhibiting envelope iscontracted about the part without materially changing the sizetolerances thereof. Furthermore, I have provided a parts treating (washand coating), apparatus of a structural character such that heat bothfor parts washing purposes and parts coating purposes is inherentlygenerated by operation of the apparatus, making it unnecessary to employextraneous heat devices. In addition, I have provided a combinationparts washing and corrosion inhibitor applying apparatus thatrecirculates the solution containing the washing chemicals and corrosioninhibiting chemicals, both in the interests of economical operation andto generate and store heat to aid the washing action.

What is claimed is:

1. In a parts treating apparatus, a housing having a parts dryingcompartment, a parts carrying pervious belt passing through saidcompartment, a blower, a plenum chamber having a plurality of nozzlesdischarging air downwardly onto said belt, and a second plurality ofnozzles discharging air upwardly against the underside of said belt, theforce of air from said first plurality of nozzles impinging the uppersurfaces of the parts on said belt being greater than the force of airfrom said second plurality of nozzles impinging against the undersidesof said parts to hold the parts to said conveyor by the forcedifferential, means operable to move said first plurality of nozzlesvertically to change the force (litterential for ditferent parts, avertically movable support for said first plurality of nozzles, and abellows connecting said first plurality of nozzles to said plenumchamber.

2. In a parts treating apparatus, a housing having an inlet and anoutlet, a blower having an intake connected to the outlet of saidhousing, a fluid pervious parts conveying belt passing through saidhousing, a plenum chamber within said housing having a plurality oflower air outlets directed against the underside of said belt, aplurality of nozzles externally of and spaced from said plenum chamber,said nozzles directed toward and disposed adjacent the upper side ofsaid belt, a vertically adjustable support carrying said nozzles, and abellows connecting said nozzles communicatively to said plenum chamber.

3. In a parts treating apparatus, a housing having a parts dryingcompartment, a parts carrying pervious belt extending through saidhousing having opposite side retaining flanges, a blower having an airintake in communication with said housing, a plenum chamber within saidhousing having an inlet in communication with the outlet of said blowerand having a plurality of air outlets directed toward and adjacent theunderside of said belt, a pervious guard overlying said conveyor withinthe confines of said flanges and vertically movable, a plurality ofnozzles carried by said guard directed to discharge downwardly onto saidconveyor, and a bellows connecting said nozzles communicatively to saidplenum chamber.

4. In a parts drying apparatus, a housing, wall means within saidhousing separating a plenum chamber from an outlet chamber, a perviousparts conveyor extending through said outlet chamber, a lower pluralityof air flow restricting apertures in said wall means arranged to directair upwardly at parts on said conveyor, an upper and vertically movablewall of said wall means having a plurality of fiow restricting aperturesdiverted downwardly at the parts on said conveyor, vertically movablesupporting means extending through said outlet chamber supporting saidvertically movable wall, said wall movable to change the elfectivepressure diiferential of the air impinging opposite sides of the parts,and a damper in said plenum chamber controlling fiow only to the lowerapertures.

5. In a parts treating apparatus, a housing, a pair of spaced parallelsupporting members mounted on and extending horizontally through saidhousing, a pervious parts carrying conveyor mounted on and extendinghorizontally between said supporting members through said housing, saidconveyor having flexible sides, outwardly disposed slideways on saidsupporting members and slidably supporting and guiding said conveyor,inwardly disposed guard members on said supporting members and extendingdownwardly into overlapping relationship with the sides of saidconveyor, a vertically movable support overlying said conveyor andslidably received and guided by said inwardly disposed side members, aplurality of nozzles carried by said vertically movable support andarranged to direct fluid at parts on said conveyor, and means operableto move said support vertically to adjust the position of said nozzlesrelative to said conveyor.

6. In a parts treating apparatus, a housing including side and bottomwalls, a partition within said housing dividing the interior thereofinto a plenum chamber having an air inlet and an outlet chamber, ablower in communication with said air inlet to maintain air pressureWithin said plenum chamber in excess of atmosphere pressure, a pair ofspaced parallel supporting members extending through said outletchamber, an air pervious conveyor extending through said outlet chamberand slidably guided by and between said supporting members, saidpartition including a horizontal portion spanning said supportingmembers beneath said conveyor and having a plurality of outlet ports incommunication with said plenum chamber to direct air upwardly at theconveyor, a horizontal upper plate overlying said conveyor between saidsupporting members and having a plurality of air ports in communicationwith said plenum chamber to direct air downwardly at said conveyor, saidplate spaced from said supporting members forming air outletstherebetween in communication with said outlet chamber.

7. In a parts treating apparatus, a housing, having an air inlet and anair outlet, a pair of spaced apart parallel supporting members extendingthrough said housing, partition means within said housing cooperatingwith said supporting members between the inlet and outlet to divide theinterior of said housing into a plenum chamber and an outlet chamber anda parts treating chamber intermediate said plenum and outlet chambers,an air pervious parts conveyor extending through said parts treatingchamber and slidably supported on said supporting members, saidsupporting members forming the side walls of said parts treating chamberand said partition means spanning said supporting members to form thebottom wall of said parts treating compartment, said bottom wall havinga plurality of apertures establishing communication between said plenumchamber and said parts treating chamber, a vertically movable platepositioned between said supporting members and cooperating therewith toform the top wall of said parts treating chamber, said plate having aplurality of apertures for inlet of air into said parts treating chamberand spaced from said supporting members to provide slotted air outletsconnecting said parts treating chamber to said outlet chamber, and abellows seal between said wall and said partition means congecting theapertures in said plate to said plenum cham- References Cited in thefile of this patent UNITED STATES PATENTS 826,300 Wilson July 17, 19061,080,704 Lilleberg Dec. 9, 1913 1,090,845 Goss et al. Mar. 24, 19141,770,991 Oflenbacher July 22, 1930 1,932,827 Morris et al Oct. 31, 19332,107,933 Crockett et al. Feb. 8, 1938 2,250,238 Smith July 22, 19412,305,655 Woolford Dec. 22, 1942 2,347,684 Hatch et a1 May 2, 19442,412,138 Fink Dec. 3, 1946 2,465,161 Little Mar. 22, 1949 2,764,170Messler et al. Sept. 25, 1956

